1. Field of the Invention
The invention relates to signal lamp assemblies in general and to vehicular signal lamp assemblies in particular.
2. Description of the Prior Art
A signal lamp mounted on the rear of a motor vehicle or also a traffic light under unfavorable conditions can be irradiated by an outside light source, for instance by the sun, in such a manner that when the lamp is off, a misleading colored reflection is caused which makes the lamp appear to be on. For traffic safety reasons, this outside or phantom light should be prevented as far as possible. Three kinds of phantom light may occur: the real colored phantom light having a signalling effect created by reflection on the optical system of the lamp glass; the mirror phantom light created by reflection on the reflector itself which also has a colored signalling effect; and the reflected-light phantom which is created by reflection on the glass surface. The reflected light phantom is a white reflex not having a direct signalling effect. In connection with the two first-mentioned kinds of phantom light, the colored signalling effect is supported, however.
In order to reduce this phantom light behind the lens of a light according to the French Pat. No. 610 148, horizontally extending diaphragms were incorporated. By this measure, however, only the mirror phantom light can efficiently be overcome. Especially in extreme cases, for instance upon very intensive solar irradiation, this lamp still causes wrong signalling effects because of the still existing real phantom light.
It is also known from German Pat. No. 1,223,279 that tilting the lens will reduce the reflected light phantom and thus, the white reflex. However, tilting the lens does not reduce the two first mentioned kinds of phantom light.